Remove the ability of webpages to specify strings for the onbeforeunload dialog.

content/browser/frame_host/render_frame_host_impl.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_
 #define CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 605 matching lines @@
   void OnRenderProcessGone(int status, int error_code);
   void OnContextMenu(const ContextMenuParams& params);
   void OnJavaScriptExecuteResponse(int id, const base::ListValue& result);
   void OnVisualStateResponse(uint64_t id);
   void OnRunJavaScriptMessage(const base::string16& message,
                               const base::string16& default_prompt,
                               const GURL& frame_url,
                               JavaScriptMessageType type,
                               IPC::Message* reply_msg);
   void OnRunBeforeUnloadConfirm(const GURL& frame_url,
-                                const base::string16& message,
                                 bool is_reload,
                                 IPC::Message* reply_msg);
   void OnTextSurroundingSelectionResponse(const base::string16& content,
                                           uint32_t start_offset,
                                           uint32_t end_offset);
   void OnDidAccessInitialDocument();
   void OnDidChangeOpener(int32_t opener_routing_id);
   void OnDidChangeName(const std::string& name, const std::string& unique_name);
   void OnEnforceStrictMixedContentChecking();
   void OnDidAssignPageId(int32_t page_id);
@@ skipping 308 matching lines @@
 
   // NOTE: This must be the last member.
   base::WeakPtrFactory<RenderFrameHostImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_